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Preparation of 2-substituted 1,3,4-thiadiazoles and mesoionic 1,3,4-thiadiazole[3,2-c]quinazolines from 4H-3,1-benzothiazine-4-thiones or 3-amino-4(3H)-quinazolinethiones

✍ Scribed by Molina, Pedro ;Arques, Antonio ;Cartagena, Inmaculada ;Alías, María Asunción ;de la Concepción Foces-Foces, María ;Cano, Felix Hernandez

Publisher
John Wiley and Sons
Year
1988
Tongue
English
Weight
756 KB
Volume
1988
Category
Article
ISSN
0947-3440

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✦ Synopsis

Reaction of 4H-3.1-benzothiazine-4-lhiones 1 with S-methylisothiosemicarbazide hydroiodide yields bamino-1.3.4-thiadiazoles 2 insteud of the espected 1.2,4-triazolo[3,2-c]quinazolines. Structures of compounds 2 have been established by mcans of '>C-N M R analysis and X-ray crystallography. 3-Arnino-4(3/f )-quinazolinethiones 4 react with ketcne dithioacetals 5 to give the new mesoionic t,3,~thiadiazolo[3.2-c]quinazolinylium-2-methanides 6 which undergo ring opening by the action or hydrochloric acid to givc z-methylene-1,3.4-thiadiamles 7. Compounds 2 are convcrted into the corresponding oxygen analog 9 by treatment with hydrochloric acid.

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